The invention relates to a manually operated ejector device for containing a cartridge loaded with viscous material, having a chamber with a front end adapted to contain the cartridge and a back end, a piston disposed in the chamber for engagement in the cartridge, a handle arranged at the back end of the chamber, and a lever displaceable relative to the chamber and the handle for driving the piston in order to drive the latter in its longitudinal direction toward the front end of the chamber.
Such ejector devices are disclosed, for example, in U.S. Pat. No. 5,489,207 or in U.S. Pat. No. 4,472,141. The cartridge placed in the front end of the chamber contains a viscous dental material, for example for filling dental cavities, which is ejected by means of the piston of the ejector device and forced into a dental cavity. For this purpose the piston attacks the back end of the stopper disposed in the cartridge and closes same, which upon the forward movement of the piston is also forced forward and at the same time ejects the viscous material from the outlet tip at the forward end of the cartridge. The travel stroke of the piston is limited by the limited length of displacement of the stopper of the cartridge. In cases in which the cartridge is not optimally adapted to the ejector device and the length of displacement of the piston of the ejector device, or in cases in which the material in the cartridge has too great a viscosity or is more or less completely hardened, as can occur with polymerizing dental materials if the cartridge is not stored properly, the danger exists that, if the pressure exerted by the dentist on the plug of the cartridge is too great, the cartridge may be destroyed in the extreme case. In the event of such destruction, parts of the cartridge may be accelerated under high pressure into the patient's jaw and there lead to considerable injury.